Design methods are increasingly drawing attention as a key area of technology. For instance, EP-B-I 112 433 claims a method of designing a roller cone drill bit by calculating certain volumes of formation cut by each tooth in the bit and adjusting correspondingly at least one geometric parameter of the design of the bit. EP-B-I 117 894 again claims a method of designing a roller cone bit by adjusting the orientation of at least one tooth on a cone of the bit, recalculating certain ratios and trajectories and adjusting the orientation of the tooth again in accordance with a recalculated value of the tooth.
High-flux light sources such as LEDs constitute a strong source of heat. High efficiency and high reliability of the associated optical system used for shaping the outgoing light beam is a mandatory requirement. In optical systems including lenses operating on a TIR (Total Internal Reflection) approach, a compromise is usually pursued between cost, efficiency and long lifetime.
Different types of optics may be selected to that end.
A first possible selection is glass optics. These have no reliability limitations in respect of high temperatures: glass can come directly into contact with a high temperature light source without being damaged. Glass optics, however, are rather expensive and usually require an additional holder: achieving complex shapes, possibly including legs or similar formations for fixing to the rest of the light module, is generally difficult in glass optics.    A second possible selection is represented by plastics optics. These are cheap and practical, and can be easily incorporated to a single piece performing both an optical function and a self-holding function. However, operating plastics optics at high temperatures may be critical.    A third possible selection is represented by so-called silicon optics. These represent a sort of trade-off between glass and plastics, in that they are more tolerant to high temperatures in comparison to plastics, while being cheaper with respect to glass optics. However, their mechanical properties may be critical (high thermal expansion, difficulties in achieving complex and/or accurate shapes, inability to be glued).
In this scenario, plastics optics represent the preferred choice for those lighting modules intended to be manufactured in high quantities (high-volume production).